1. Field of the Invention
The present invention pertains to shaped crystalline anionic clay-containing bodies.
2. Prior Art
Examples of crystalline anionic clays include hydrotalcite, meixnerite, sjögrenite, pyroaurite, stichtite, reevesite, eardleyite, manassite, and barbertonite. Crystalline anionic clays have several applications in the catalyst field and as absorbents. For most commercial applications crystalline anionic clays are formed into shaped bodies such as spheres. In all applications where shaped bodies are exposed to severe processing conditions and environments, such as oil refinery applications, separations, purifications, and absorption processes, it is of paramount importance that the integrity of the crystalline anionic clay-containing shaped bodies is kept intact and attrition is prevented.
In the prior art, crystalline anionic clays are usually incorporated into binder or matrix material in order to obtain attrition resistant shaped bodies. Commonly used binder or matrix materials are alumina, and silica. Frequently used alumina precursors are aluminium chlorohydrol, soluble aluminium salts, and acid dispersed pseudo-boehmite; regular silica precursors are silica sols, silicates, silica-alumina co-gels, and combinations thereof.
EP-0 278 535 describes FCC additives or catalyst particles which are prepared by embedding hydrotalcite and optionally zeolite in a silica, silica-alumina or alumina matrix. To this end, hydrotalcite is slurried in a matrix precursor dispersion containing the other catalyst components or precursors thereof and subsequently spray-dried.
However, when crystalline anionic clay is embedded in a matrix, the amount of active crystalline anionic clay contained within the resulting shaped bodies tends to be relatively small. There are applications in which for performance reasons it is desired that the shaped bodies consist or mostly consist of active crystalline anionic clay. Also, by the incorporation of crystalline anionic clay into matrix material, physical properties of the crystalline anionic clay such as specific surface area, pore size distribution, etcetera may be detrimentally affected. Further, the distribution of the crystalline anionic clay within the matrix is difficult to control. Another disadvantage of having to use a matrix to obtain attrition resistant bodies is the fact that most commonly used matrix/binder materials have some chemical activity, which in certain applications can cause undesirable side reactions. For instance, one of the most commonly used binder materials in FCC catalysts and additives is silica or silica based material. These types of binders are not suitable for use in sulphur oxides removal additives, because they detrimentally affect the sulphur removal.